This application claims the benefit of Korean Patent Application No. 2001-74365 filed on Nov. 27, 2001, which is hereby incorporated by reference as if fully set forth herein.
1. Field of the Invention
The present invention relates to a liquid crystal display (hereinafter, as LCD) device, and more particularly to the liquid crystal display device having an injection opening with an improved structure in which photo-sensitive encapsulation material and sufficiently exposed with the light in order to prevent the non-hardening of the encapsulation material caused by insufficient light exposure and prevent cracks of the encapsulation material caused by a step-compensating pattern of the injection opening.
2. Discussion of the Related Art
A liquid crystal display device is a transmission flat panel display device and is applied to various electronic equipments such as a mobile phone, PDA and notebook computer. Of the flat panel display devices, the LCD is most useful because of characteristics such as light weight, smaller size and a high image quality. Moreover, as the request for a digital TV or high image quality TV and panel type TV has increased research in the field of large area LCDs is more active.
Generally, LCDs may be divided into several types based on the operation mode of the liquid crystal molecules. Of the several types the TFT (Thin Film Transistor) type (TFT-LCD) is mainly used because of the fast response time and the reduced residual image.
Referring to FIG. 1, the TFT-LCD includes a lower substrate 3, upper substrate 5 and liquid crystal layer 17 therebetween. A plurality of gate lines 11 and data lines 13 are arranged in the vertical and horizontal directions on the lower substrate 3 to define a plurality of picture elements (pixels). The gate lines 11 and data lines 13 are electrically connected with an outer driving device (not shown) through pads 12 and 14, respectively, in a non-displaying region of the lower substrate 3. A TFT 15 is disposed in each pixel. A scanning signal is applied to the TFT 15 through the gate line 11, so that the TFT 15 is switched to apply an image signal to the liquid crystal layer 17 from the data line 13.
A sealing unit 7 on which sealing material is deposited is formed at the outer portion of the lower substrate 3 and upper substrate 5, thereby the lower substrate 3 and upper substrate 5 are attached each other. As shown in the figure, a black matrix 9 is formed in a region corresponding to the sealing unit 7 to block light through the region. The black matrix 9 is formed on the upper substrate 5. Though the black matrix 9 is disposed only the region corresponding to the sealing unit 7 in the figure, the black matrix 9 may be disposed such that the area between the pixels and TFT active area to block the light through non-displaying region.
In the figure, reference numeral 20 designates a liquid crystal injection opening for injecting liquid crystal between the attached lower and upper substrates 3 and 5. After injecting the liquid crystal through the liquid crystal injection opening 20, the liquid crystal injection opening 20 should be encapsulated by encapsulation material 22. Because the encapsulation material 22 is the photo-sensitive material, the encapsulation material 22 filled inside the liquid crystal injection opening 20 is hardened by exposure to light such as ultraviolet light.
A plurality of patterns 24 are disposed at the injection opening 20. The patterns 24 are the step-compensating patterns for preventing the generation of the defection in the TFT-LCD as steps are generated by the TFT or pixel electrode (not shown) formed in the pixel region.
Hereinafter, the TFT-LCD with the above composition will be described in more detail with reference to FIG. 2. In the figure, the region of the TFT-LCD where the image is actually displayed and the liquid crystal injection opening area are separated for convenience of description.
As shown in the figure, a gate electrode 31 is formed in the display region on the lower substrate 3 and a gate insulating layer 32 is deposited over the whole substrate 3. A semiconductor layer 34 is formed on the gate insulating layer 32 and activated by the scan signal applied to the gate electrode 31 to form a channel layer. Source/drain electrodes 36 are formed over the semiconductor layer 34. The source/drain electrodes 36 are electrically connected to the pixel electrode 38 in the region of the pixel where the image is actually displayed to apply the signal from the source/drain electrodes 36 to the pixel electrode 38 when the semiconductor layer 34 is activated. A passivation layer 39 is deposited over the source/drain electrodes 36 and the pixel electrode 38.
An alignment layer (not shown) is deposited over the passivation layer 39, to align the liquid crystal molecules in the liquid crystal layer 17.
A step compensating pattern 24 is formed on the gate insulating layer 32 in the liquid crystal injection opening area. This step compensating pattern 24 compensates the step caused by the pixel electrode 38. The step compensating pattern 24 is mainly made of the semiconductor material so that the pattern 24 is formed by the same process as the semiconductor layer 34 of the TFT.
The black matrix 9, a light-blocking element, and the color filter layer 42 are formed on the upper substrate 5. As shown in the figure, the black matrix 9, which is made of the material such as Cr, CrOx or Cr/CrOx, is formed in the TFT area of the pixel region, above the gate line, the data line, and the liquid crystal injection opening area. Further, a common electrode 44 is formed over the black matrix 9 and the color filter layer 42 to operate the liquid crystal molecules of the liquid crystal layer 17 as the signals are applied to the liquid crystal layer 17 through the TFT. The alignment layer is deposited on the common electrode 44 to align the liquid crystal molecules.
Spacers 50 are scattered between the lower substrate 3 and the upper substrate 5 to maintain a uniform cell gap and then the lower substrate 3 and the upper substrates 5 are sealed. The liquid crystal is injected between the sealed substrates 3 and 5 through the liquid crystal injection opening to form the liquid crystal layer 17. Thereafter, the liquid crystal injection opening is encapsulated with the encapsulation material.
FIG. 3 shows an enlarged structure of a liquid crystal injection opening encapsulated by the encapsulation material. As shown in the figure, a plurality of step compensating patterns 24 are formed over the whole area of the liquid crystal injection opening and the encapsulation material 22 is filled at the liquid crystal injection opening area. The encapsulation material 22 is depicted as the portion hatched by points.
Although the encapsulation material 22 is not filled in the portion on the step compensating patterns 24, as illustrated in FIG. 3 to indicate clearly the encapsulation material and the step compensating patterns 24, the encapsulation material in practice is also filled on the step compensating patterns 24, as illustrated in FIG. 2.
The encapsulation material 22 includes photo-sensitive material. Therefore, the encapsulation material 22 in the liquid crystal injection opening area is exposed to light, such as UV light, to harden the encapsulation material 22 to encapsulate the liquid crystal injection opening. In the other words, the UV light must be irradiated to the lower substrate 3 and upper substrate 5. As shown in the figure, the black matrix 9 is formed on the upper substrate 5 in the liquid crystal injection opening area. Accordingly, it is impossible to expose sufficiently the encapsulation material with UV light because of the black matrix 9 blocks light irradiated through the upper substrate 5. Generally, UV light having about 300 mj/cm2 of light amount is needed to harden sufficiently the encapsulation material. However, the practical mount of UV light exposed to the encapsulation material is smaller than 300 mj/cm2 because of the blocking caused by the black matrix 9. Because of this insufficient light amount, it is impossible to harden sufficiently the encapsulation material so that the non-hardening material may flow into the displaying region and a resultant spot is generated in the display region.
Further, in case of irradiating the UV light from or through the lower substrate 3, the UV light may be blocked by the step compensating patterns 24. Thus, encapsulation material is exposed with the UV light of an insufficient amount and, as a result, the exposed encapsulation material may not be hardened. Since the encapsulation material 22 in the vicinity of the step compensating pattern 24 is cracked along the pattern 24, in addition, serious defects are generated in the liquid crystal display device.
Accordingly, the present invention is directed to a liquid crystal display device having improved structure of injection opening that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a liquid crystal display device having an improved structure of injection opening, that facilitates hardening of the encapsulation material by exposure to a sufficient amount of light because a black matrix and a step compensating pattern are not formed in the injection opening area where the encapsulation material is filled.
Another advantage of the present invention is to provide a liquid crystal display device that can prevent light-leakage phenomenon by not-forming a black matrix by attaching the region where the encapsulation material is filled to an outer case of the LCD device.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a liquid crystal display device having an improved structure of injection opening. The injection opening area is divided to two regions. Since the encapsulation material is filled only in the region where the black matrix and the step compensating pattern are not formed, blocking of light irradiation is not occurred by the black matrix and the step compensating pattern, in the light-hardening of the encapsulation material. Therefore, the perfect hardening of the encapsulation material is possible by the light irradiation of the sufficient amount of the light. The region where the encapsulation material is filled is attached to the outer case of the liquid crystal display device, thus to prevent the light transmission to the region.
Also, the present invention provides a liquid crystal display device having the above structure of the injection opening.
The step compensating pattern can be simultaneously formed with an identical material of the semiconductor layer of the thin film transistor and with metal of the gate electrode or source/drain electrode. The step compensating pattern can be formed in various shapes.
In the region where the encapsulation material is not filled, the black matrix and step compensating pattern can be formed and just a black matrix can be formed. Also, the step compensating pattern can be extended and formed to the region where the encapsulating material is filled.
It is to be understood that both the foregoing and general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.